Food Irradiation Using Electron Beams and X-Rays

Bruce MillerEBM, LLC

ISNATTSeptember, 2004

Questions

What is Food Irradiation?Is it Safe?Why is it Effective?How is it Done?What are Important Applications?Will it become an Important Food Processing Technique?

What is Food Irradiation?

Definition: The use of ionizing radiation (electrons, x-rays, gamma rays) to decrease the population of, or prevent the growth of, undesirable biological organisms in food.

Radiation Sources:

Radioactive Isotopes (Cobalt-60)Electron Accelerators (electron beams and x-rays)

Comparison:1 million curies of Co60 = 15kW (e-beam)

= 185kW (x-rays)

We already buy many irradiated products

SpicesBand-AidsPet TreatsCosmeticsBaby BottlesComputer ChipsFeminine ProductsBaby DiapersWound Care50% of all medical devicesFood Products

Principle Applications of Food Irradiation

Enhanced Food Safetyeliminate harmful food-borne bacteria (e-coli, salmonella, listeria) (typically 1-2 kGy)– US CDC estimates are

5,000 deaths325,000 hospitalizations76 million cases of illness

Disinfestation to kill fruit flies and other pests (typically < 0.5 kGy)– Eliminate need for chemical fumigation

Reduced food spoilage to extend shelf-life (0.5-10 kGy)

Inhibit sprouting, etc. (0.1-1 kGy)

Sterilization (>42.7 kGy)

– Patients with compromised immune systems; NASA astronauts

Listeria

E. Coli

Salmonella

Foods Currently Approved for Irradiation in the USA

Product

Approval Date

Max. Dose (kGy)

Wheat & wheat flour 1963 0.50 Dry enzyme preps 1985 10.0 Pork 1985 1.0 Fruits & Vegetables 1986 1.0 Spices & dry seasonings 1986 30.0 Poultry 1992 3.0 Red Meat (fresh/frozen) 2000 4.5/7.0 Shell eggs 2000 3.0 Seeds for sprouting 2000 8.0 Animal Feed & Pet Treats 2001 50.0

Petitions Under Review by FDA/USDA

Processed Foods– Submitted by NFPA in Aug. 1999– Hot dogs, deli meats, RTE meat, processed fruits &

vegetables, fruit juicesMolluscan shellfish– Submitted by NFI in Oct. 1999

Crustaceans– Submitted by NFI in Feb. 2001

International Approvals

42 countries have issued approvals 140 foods have been approved by at least one countryConflicts of dose or food descriptions among countriesHarmonization is progressing by regionDoses vary greatly by region and country

Labeling

Retail• Radura, plus “Treated with / by

Irradiation” – (Irradiated for food safety)

• Claims: Reduced, Eliminated, or Free (OK if substantiated)

• If treated product used as an ingredient, identify in Ingredient Statement

Foodservice• On case to establishment• No requirement to inform consumer

Label Regulations

Is Irradiated Food Safe?• Induced radioactivity is of no concern,

provided:Ee < 10MeV; Ex < 5 MeV

• Compounds formed by irradiating food are essentially the same as those produced by other preservation methods (i.e., cooking)

• “The Study Group concluded that food irradiated to any dose appropriate to achieve the technological objective is both safe to consume and nutritionally adequate.” - WHO TR 890, 1999

• No evidence exists that pathogenic bacteria become more virulent when irradiated

• “there is no other known means to kill deadly bacteria such as E. Coli 0157 H:7 in raw ground beef” - USDA

Support for Irradiation TechnologyProminent health and medical organizations support the use

of irradiation technologyProminent health and medical organizations support the use

of irradiation technology

American Medical Association

AMERICAN DIETETIC ASSOCIATION

Two Supporting Points of View

“An overwhelming body of scientific evidence demonstrates that irradiation does not harm the nutritional value of food, nor does it make the food unsafe to eat. … Food irradiation is a logical next step to reducing the burden of foodborne disease in the United States.” (US Centers for Disease Control)

“Food irradiation is possibly the most significant contribution to public health to be made by food science and technology since the pasteurization of milk.” (World Health Organization’s Food Safety Unit)

Opposing Viewpoint(Organic Consumers Association)

Irradiation damages the quality of food.Science has not proved that a long-term diet of irradiated foods is safe for human health.Irradiation covers up problems that the meat and poultry industry should solve.Irradiation doesn’t provide clean food.Irradiation using radioactive materials is an environmental hazard.Electron-beam irradiation today means nuclear irradiation tomorrow.

What does organically grown mean? Where do the plants get theirnutrients?

Effects of Ionizing Radiation on Micro-organisms

Number of interactions permolecule depends on molecularsize

Nm = 10-7 GMwD(kGy)

G = “G-Value” – number of events per 100 eV

M = molecular weight= 180 for glucose; 109 for DNA!

Ionizing radiation preferentiallydisrupts DNA because of itsenormous size.

(Much smaller food constituent molecules are largely unaffected.)

Effects are stated in terms of the absorbed “dose”

Dose = Energy absorbed per unit massDose is typically measured in kiloGray

1 kGy = 1 kJ/kgTemp. rise is 0.25 oC.

Effects on Food Constituents

CarbohydratesWeakening of large structural molecules (cellulose) at high doses (>10 kGy)

Lipids (fats and triglycerides)Oxidation of fats can lead to off-odors (>3-5 kGy)

ProteinsWeakening of structural proteins at high doses (>10 kGy)Denaturation at high doses (> 10 kGy)

Vitamins20% loss of thiamine at 3 kGy

Far less impact than most other food processing techniques (cooking, pasteurization, freezing, dehydration, etc.)

Establishing Target Dose Values

Effects of ionizing radiation are characterized by absorbed dose.– 1 kGy = 1 kJ/kg

D-value = The dose required to achieve a 1 order of magnitude reduction in the microbial population. (Established by scientific testing.)– E.Coli 0157:H7, Salmonella,

Listeria ≈ 0.25 – 0.70 kGy

Typical food safety doses = 5 log reduction (99.999%) = 1.25 kGy minimum required dose for e.coli

Dose

543210

-1-2-3-4-5

Logs

Electron-Beam / X-Ray TechnologyThe primary goal is to deliver the minimum required dose to all parts of the product. There are three essential pieces of technology:

• A high-energy electron beam is generated by the accelerator system

• The beam is uniformly swept across the product using a magnetic beam scanner

• A thin exit window (Ti) is used for direct electron irradiation; x-rays are generated with a high-Z converter

• Product is passed through the scanned beam in a highly controlled manner by the material handling system

Kinetic Energy Considerations

To avoid food activation, the electron kinetic energy is limited to 10 MeV for electron beamprocessing, and 5 MeV for x-ray processing.For electron beams, penetration depth scales linearly with kinetic energy.For x-rays, the generation efficiency scales linearly with kinetic energy. (8% @ 5 MeV)(Usually) operate at the maximum permissableenergy.(Usually) implies a microwave accelerator.

Accelerator System Key Components

PulseTransformer

Modulator

HVPS

PFN & Thyratron

Klystron

Accelerator

Load

rf windowElectron gun

Circulator

Directionalcoupler

Water cooling system

Vacuum system

Gas pressure

Control System

Scanner

High-Power (SB5/150) Linac

Beam Scanning System

Beam is “uniformly”scanned over the product using magnetic deflection.

B

Material Handling System Description

MH system moves product at a constant rate through the irradiation zone with minimal space between product carriers or packages.There can be three conveyor elements in the MH system– High speed feed conveyor (flexible loading and unloading)– Closing conveyor (minimizes space between product

carriers)– Process conveyor (moves product carriers through the

irradiation zone at a precise rate)The product flow is monitored and controlled by a process control system.

Front Surface Dose

Dose is the key parameter that links the accelerator system, the scanner and the conveyor system.

Electrons (10 MeV):

Dfs = 1.8x106 I(A) / [v(cm/s)w(cm)]

X-Rays (5 MeV):

Dfs = {3.4 P(kW) / [vw]} e-0.012zc(cm)

v

w

scan horn

conveyor

Depth-Dose Distributions

Single-Sided E-Beam Irradiation at 1.0 gm/cc Density

10 MeV Dose / DepthSingle Sided

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

0.0 0.5 1.0 1.5 2.0 2.5 3.0

Penetration (in.)

Rel

ativ

e D

ose

Double-Sided E-Beam Irradiation at 1.0 gm/cc Density

10 MeV Dose / DepthDouble Sided

Max/min = 1.36

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

0.0 0.4 0.8 1.2 1.6 2.0 2.4 2.8 3.2 3.6

Penetration (in.)

Rel

ativ

e D

ose

If the areal density (density multiplied by thickness) exceeds 8.5 g/cm2 , must use x-rays (> 20 g/cm2).

Double-Sided X-Ray Irradiationat 1.0 gm/cc Density

Product Throughput Rate Estimates

Processing rate (mass per unit time) = effective rate of energy absorption (power) divided by the required dose.

dM/dt (kg/s) = η x P(kW) / D(kGy)

η (efficiency) = 0.5 (e-beam, 10 MeV)= 0.03 (x-ray, 5 MeV))

Example 1: P = 15 kW e-beam, D = 1.5 kGy (ground beef)dM/dt = 5 kg/s = 40,000 lbs/hr!

Example 2: P = 150 kW x-ray, D = 5 kGy (spices)dM/dt = 0.9 kg/s = 7000 lbs/hr

Food Processing Facility Overview

warehouse

loading dock

unload dock

HVAC ozoneexhaust

load station

acceleratorand scanner

modulator room

electrical substation

double-pass material handling system

process table

unload area

dosimetrylaboratorycontrol room

load area

radiation shield

E-Beam and X-Ray System Configurations

E-Beam X-Ray

Horizontal Beams;

O/H P&F;

Roller w/ Translation

Vertical Beams;

Roller Conveyor

Electronic Food Irradiation Facilities

Location Accelerators(KE/P)

MaterialHandling

Throughput(lbs/hr)

Application

Sioux City 10/15 (x2-u/d)5/15

Roller2-p w/ transl.

60,000@2kGy1500@2kGy

Food Safety

Hawaii 5/15 O/H P&F2-p w/rot

6000@0.5 kGy Disinfest.

Viet Nam 5/150 O/H P&F (x)2-p w/rot

6000@5kGy Food Safety

Los Angeles

10/15 (x2-u/d)5/15 (x2)

Roller (e)O/H P&F (x)2-&4-p w/rot

60,000@2kGy1200@5kGy

Food Safety

Texas A&M

10/15 (x2-u/d)5/15

Roller2-p w/ transl.

- Research

Costs/Pricing

Capital investment is significantAccelerator systems in range of $1-2MTotal facility costs in range of $5-10MAmortization of capital investment is usually the largest yearly cost item. (Dwarfs cost of electricity.)

Breakeven processing price is usually in the range of $0.01 – 0.10 per pound.

What Does The Future Hold?

Market SizeConsumer AcceptanceGovernment RegulationsImpediments to Industry Growth

Anti-nuclear lobby (isotopes)Equipment reliability (machine sources)Large Food Producers/UsersCost/Pricing

Estimated Market SizeEstimated Worldwide Food Production Volume

(millions of pounds)

Product US International Total

Ground Beef 9,000 10,000 19,000

Poultry 35,000 100,000 135,000

Processed Meats 25,000 N/A 25,000

Seafood 12,000 250,000 262,000

Fruits/Vegetables 65,000 1,300,000 1,365,000

Total 146,000 1,660,000 1,806,000

Business opportunity depends on “public acceptance.”

Modest adoption of food irradiation could require significant capital investment.

Some of the implied opportunities will not represent good business ventures.

Opinions on Irradiated Foods

Awareness is high but understanding is lowInformed consumers are more acceptingPurchase intent is relatively highMeat & poultry seen as the likeliest candidates for irradiationConsumers are turning to the government for broader use of irradiation for food safety

Product Acceptance

Consumers cannot differentiate between irradiated and non-irradiated foods

Strong evidence of commercial success where irradiated foods are available in restaurants

Government/Regulatory Factors

FSIS considers e.coli O157:H7 to be an adulterant – no organisms permitted!“there is no other known means to kill deadly bacteria such as E.Coli 0157 H:7 in raw ground beef” – USDA– Irradiation of fresh ground beef is not mandated.

Seafood and Ready-to-Eat petitions are languishing –their approval is not a high priorityCongress is sensitive to letter-writing campaigns of the “anti-nuclear” lobbyIrradiation is still considered a food “additive,”, instead of a process.

Waiting on government regulations to spur industry growth is a losing strategy.

Who is the Preferred Customer for Food Irradiation Services?

Large producers/users are not so interested.– Irradiation will not increase their market share– They can handle recalls and lawsuits– Irradiation disrupts their traditional ways of doing

business.Passive resistance– studies

Active resistance– High surcharges to consumers because food is

“safer”

Suggested Path Forward

Technology– Get costs under control– Improve processing efficiency– Improve machine reliability

Marketing– Concentrate on markets in which irradiation

provides an economic incentive– Quarantine treatment opens new markets– Extended shelflife allows longer shipping times,

and access to new markets– Strong, active support of the Ready-to-Eat petition.

For Further Questions or Discussion

RMiller857@aol.com

505-239-6115 (cell)505-266-3430 (fax)